Calculate the magnitude and direction of the torque

  • #1
6
0

Homework Statement


[/B]
a) (a) Assuming the HCl molecule consists of point-like ions (H+ and Cl) separated by 1.0 * 10^-10m, find the dipole moment of the molecule.
b) Calculate the magnitude and direction of the torque exerted on this dipole if the molecule is subjected to an external electric field of 4.0*10^6 N C^(-1), when the angle between the field direction and the axis of the molecule is 45 degrees.


Homework Equations


torque = pEsin(theta)

The Attempt at a Solution


a) Assuming magnitude of charge (Q) on either ion is 1.6*10^(-19)C then using the formula for the dipole moment p = Qd I get an answer of 1.6*10^(-29)Cm.
b) For the second part of the question I'm not too sure how to find the direction of the torque. I have attempted to work out the magnitude using the relevant equation stated above and got 4.5*10^(-23)Nm but I am not too sure about this answer.

P.S I am very sorry for the sloppy writing I understand it may be hard to understand what I mean but I've spent so much time doubting my answer that now I've confused myself! Any help would be appreciated!
 
Last edited by a moderator:

Answers and Replies

  • #2
10
4
Your answer seems right.
In order to incorporate direction into your formula
we have
τ = p×E
so if E is 45 degrees counterclockwise of p then τ is counterclockwise
if E is 45 degrees clockwise of p then τ is clockwise

Your problem doesn't state whether it is 45° clockwise or counterclockwise but either way, the dipole will rotate so that p is aligned with E.
 

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